Prostaglandins increase the effect of oxytocin and vice versa. The contractions should be carefully monitored if oxytocin is given after a prostaglandin dose.

Syntometrine may enhance the blood pressure raising effect of vasoconstrictors (medicines given to constrict the blood vessels).

Some inhaled anaesthetics used for general anesthesia, such as cyclopropane and halothane, may reduce the effect of oxytocin and ergometrine. There may also be an increased risk of a drop in blood pressure and abnormal heart beats if oxytocin is given with these general anesthetics.